Chapter 2. NIKE-X SYSTEM

Unlike
its predecessor, NIKE-ZEUS, and its successors, SENTINEL and
SAFEGUARD, NIKE-X was not a single ABM system concept. Rather, it
should be thought of as a collective term to cover a number of
studies and exploratory developments aimed at leading from the then
outmoded NIKE-ZEUS to the next generation ABM system. Figure 2-1 maps
the more significant NIKE-X System Studies and supporting R&D
activities discussed in this chapter.

NIKE-X
began about 1960, when it became apparent that by the early 1970s the
USSR might be able to mount a high-traffic attack against the U.S. By
1963 it was accepted that the USSR had the technological ability and
the expressed intention to develop at least a parity in warhead yield
with the U. S. The sophistication of USSR mid-70s ICBM offensive
systems was not readily predictable; conservative assumptions
included chaff, decoys, and Electromagnetic Counter-measures (ECM) as
penetration aids.

This
escalation of the assumed USSR threat was a breakpoint in the general
approach to the NIKE-ZEUS development. Until then the ZEUS system had
been based on earlier assumptions of much lower USSR capabilities.
The NIKE-ZEUS system had been designed to defend population and
industrial centers from a relatively light attack. For example, in
tracking targets and missiles, only one target and missile could be
tracked at one time by the ZEUS Target Track Radar (TTR) and Missile
Track Radar (MTR), respectively. Multiple targets and missiles were
handled by multiple pairs of TTRs and MTRs. Adding single
target-interceptor tracking subsystems was not a cost-effective
response to escalation of the predicted threats; fundamental changes
in radar data-gathering techniques were required. Furthermore, the
best large-scale computers of the time were not capable of handling
the data processing loads associated with the newly expanded threat
concepts.

Fortunately,
as the threat expanded, solid-state technology evolved enough to make
possible two important improvements in ABM system capability. One of
these was the development of large electronically steered,
phased-array radars capable of tracking many targets simultaneously.
The other was the development of high-reliability,
very-large-throughput data processors for ABM needs. The combination
of escalating threat and expanding technology gave impetus to the
NIKE-X high-traffic ABM concepts.

The
initial thrust of NIKE-X was to develop a base of knowledge from
which the development effort could be started. For example, the MAR-I
at White Sands Missile Range (WSMR) explored array radar designs to
develop a firm technical base for NIKE-X. The Reentry Measurements
Program (RMP A and B), in which NIKE-X radars observed reentries of
IRBMs and ICBMs, was another very large, technically challenging
effort that helped to establish the NIKE-X data base. RMP is
discussed in detail later in this chapter.

Figure
2-1. Map of the NIKE-X Era

NIKE-X CONCEPT

The
first NIKE-X System Study, in 1963, considered a terminal defense for
the larger U.S. cities against the sophisticated USSR attack
postulated for the mid-1970s. It was unreasonable to make the defense
impenetrable; the objective was to mitigate damage and thus deprive
the offense of attractive attack opportunities.

In
developing concepts to meet these city defense objectives, several
major subsystems were defined. The Multifunction Array Radar (MAR),
which performed search, track, and discrimination, was the
centerpiece of city defense. The Missile Site Radar (MSR) and a
high-acceleration, atmospheric interceptor, the SPRINT, formed a team
for fast reaction, high-traffic, terminal interception of attacking
ICBMs. The MAR, MSR, and SPRINT were also responsible for
self-defense of the ABM facilities.

At
the beginning of NIKE-X, a number of major elements were carried over
from ZEUS: the Target Track Radar (TTR), the Missile Track Radar
(MTR), and the ZEUS missile.

After
the studies of deployment and system effectiveness, the defense of
cities smaller than our 50 largest was studied next. This led to an
enhanced role for the MSR — the defense of smaller cities. For
cost reasons, the MSR, in addition to interceptor track and guidance,
was assigned many roles similar to those of the MAR, such as search,
track, and target designation. Where coverage with the reduced
resources of the MSR was consistent with the small city requirements,
the autonomous MSR served as a cost-effective duplication, on a
lesser scale, of the MAR.

By
the mid-1960s, system studies concentrated on reducing the cost of
defense and improving its cost effectiveness. One approach,
designated TACMAR, was a reduced-power variation of the MAR that
could, if the need arose, grow to full MAR capability. By 1968, the
city defense concepts were reassessed, and the decision was made to
shift the defense objective to an area defense against relatively
light attacks. The 1-67 Study addressed this less costly area defense
objective. With this shift in emphasis, ABM moved away from the city
defense concept, thus removing the requirement for MAR/TACMAR. As a
result, a much different kind of sensor was required; one that could
detect, track, and designate targets above the atmosphere at very
long ranges. This role was first assigned to a new VHF radar, which,
late in the NIKE-X period, became the UHF Perimeter Acquisition Radar
(PAR). The interceptor chosen for area defense was an extension of
the ZEUS missile, called SPARTAN.

In
summary, the light area defense concept was developed through various
deployment studies, beginning with NIKE-ZEUS, which was a pure area
defense system. The ZEUS area defense concept was partially
incorporated into NIKE-X and became a separate concept in the Nth
Country and 1-67 Studies. The chronological sequence of area defense
studies and postulated deployments included NIKE-ZEUS, Nth Country,
DEPEX, 1-67, SENTINEL, and finally SAFEGUARD. The other variant,
point defense, is discussed next.

DEFENSE
OF STRATEGIC FORCES-TERMINAL/POINT DEFENSE

By
the mid-1960s, the NIKE-X program had two distinct defense
objectives:

Defense
of strategic forces moved toward hardened defensive and offensive
sites. The objective was to present significant, obvious
uncertainties to the offense planner and hence produce influential
deterrence. These terminal defense efforts led to a series of system
studies: Hardpoint, Hardsite, and VIRADE. An early study1
of the defense of U. S. strategic forces took place in 1963-64. For
this study, two configurations were considered: one for defending
hardened sites near defended urban areas (called HSD-I) and the other
for autonomous defense of isolated sites (called HSD-II). The
study sought to protect command and communication facilities and the
U.S. strategic offensive force, including clusters of ICBMs and SAC
bases.

Under
joint directorship of the Army and the Air Force, a later study2
emphasized an active defense dedicated to hardened ICBM silos which
hold the Minuteman strike force. The study concentrated on technical
tradeoffs between parameters in designing the various subsystems and
drew conclusions about the relative effectiveness of tactics,
deployments, and required technology.

The
VIRADE (Virtual Radar Defense) mobile system was proposed as a way to
increase radar attack price by presenting to the attacker a large
number of possible locations for each available system. The proposed
system is discussed later in this chapter.

BASIC NIKE-X SYSTEM

Threat
Description

NIKE-X
was designed to counter a high traffic, decoyed attack that included
active jammers and low-visibility Reentry Vehicles (RVs).3
Various threats were postulated to guide the design work and to serve
as models for projecting effectiveness. These threat models used USSR
ballistic missile characteristics, estimated on the basis of known
technology and intelligence information, and were defense
conservative.

The
RV was assumed to have low radar cross section and high ballistic
coefficient.4 The USSR would use low cross section, in
combination with chaff or jammers, to mask the exact RV position.
Multiple warheads were considered likely, and an RV that maneuvered
evasively in the terminal trajectory phase was considered possible.
Assumed yields ranged from several kilotons to many megatons,
depending on the mission of the particular RV. Chaff was considered a
standard countermeasure to obscure the attack outside the atmosphere.
In addition, "fast chaff" was postulated as a number of
simple dipoles, with a moderately high ballistic coefficient, serving
as traffic decoys at high altitudes. More sophisticated decoys would
simulate RVs down to relatively low altitudes. They would match the
radar cross section and ballistic coefficient of the RV down to an
altitude which could force the defense to engage them as potentially
dangerous. Active jammers were also assumed as penetration aids.

System
Architecture and Operational Concept

System
Elements

During
its development, which extended through 1966, NIKE-X and its defense
objectives changed several times, which in turn produced major
changes in configuration. In its original form, NIKE-X used two types
of phased-array radars (MAR and MSR), two defensive missiles (SPRINT
and ZEUS), and a modular, multiprocessor data processing system. In
addition, the NIKE-ZEUS Target Tracking Radar and Missile Tracking
Radar remained parts of NIKE-X until it was verified that the
phased-array MAR had the accuracy needed for long-range intercepts.

The
L-band MAR was to be installed in densely populated urban/industrial
areas (see artist's view of city defense in Figure 2-2) for (1) the
long-range search needed for attack recognition and (2) the quick
reaction, high-traffic capability needed for terminal defense.
Associated with each MAR was a Defense Center Data Processing System
(DCDPS) which controlled the MAR and any MSRs in the same area. With
the MAR as its principal sensor, the DCDPS performed all urban
defense functions: detecting, tracking, and evaluating threats,
planning the battle, and guiding defensive missiles.

For
terminal defense, NIKE-X relied on SPRINT, a relatively small,
high-acceleration missile, which is described more fully in Chapter
9. SPRINT is aerodynamically guided (except for first-stage boost)
and designed for intercepts within the atmosphere. Its warhead has
maximum lethality at its operational altitudes. For terminal defense
of a large area, SPRINT missile farms were emplaced at various points
about the defended urban center, particularly forward of the MAR.

Figure
2-2. City Defense

The
S-band MSR originally had two functions: missile tracking and target
tracking at relatively short ranges. A missile tracker was needed at
the forward SPRINT farms because the MAR would generally not have a
line-of-sight to the SPRINTS at launch. The MSR could launch and
guide the SPRINT to intercept, or launch and then transfer control to
the MAR when the SPRINT came into the MAR's view. The MSR could track
targets at relatively short range and look behind nuclear fireballs
that obscured MAR coverage. Also, it could either look behind or
permit triangulation on jammers, and generate additional tracks when
required by traffic levels.

By
mid-1964, a Small City Defense (SCD) concept was firmly established
as part of NIKE-X. In this concept, the MSR role was expanded so that
it was deployed either singly or in groups to provide a somewhat
autonomous defense of small urban areas. The SCD also had a smaller
version of the DCDPS, called a Local Data Processor (LDP). In
addition to the target and missile tracking functions originally
assigned to the MSR, the MSR-LDP combination carried on search,
verification, and limited threat evaluation.

The
ZEUS missile was included in NIKE-X whenever intercepts were required
at extended ranges and high altitude. It was a somewhat modified
version of the standard missile developed for NIKE-ZEUS. Although it
was conceived that NIKE-X would defend concentrated urban areas and
rely on close-in use of the SPRINT missile, several uses were
envisioned for the ZEUS missile. Its exoatmospheric capability could
"break up" a heavily cluttered attack, particularly if
salvos of ZEUS missiles were launched. For attacks simpler than those
expected against urban centers, such as submarine-launched missiles
aimed at suburban or peripheral targets, the ZEUS missile could
extend the effective coverage of a NIKE-X installation. Other
potential uses for the ZEUS missile included intercept of a
three-quadrant ballistic missile approaching from the south and
intercept of low altitude satellites.

Operational
Concept

NIKE-X
was designed as a defense against a massive, sophisticated ballistic
missile attack. All phases of the defense, from surveillance to
missile guidance, were controlled by stored programs in the DCDPSs
and LDPs. Man's role in the defense was regarded as one of augmenting
and modifying system responses, once he had released the defending
missiles. Although advantage would be taken of any attack that was
simpler than expected (e. g., without decoys or chaff), the
operational concept envisioned the decoyed, chaff-obscured attack,
possibly also masked by active jammers.

The
system's radars — the MAR supplemented by the MSR — would
perform constant surveillance against attack from any direction, with
emphasis on expected attack corridors. MAR would detect the large,
chaff-obscured threat complexes, or "clouds, " as they
appeared above the radar horizon and start to track them. Depending
on attack geometry, a track could be an individual object or a whole
threat cloud.

Engagement
planning would begin as soon as a threatening target was detected.
The first action would be to determine the feasibility of launching
ZEUS missiles. They would be launched to disperse chaff, disable
jammers, disorganize or destroy decoys, and kill warheads. Any
information from adjacent MARs with a side look at the threat cloud
would facilitate ZEUS engagement planning. The next step would be to
plan the SPRINT response. As the threat cloud entered the atmosphere,
a "threat tube" would be defined. This tube would have a
circular or elliptical cross section and define the envelope formed
by the reentry trajectories of threatening objects in the cloud.

MAR
used a "monosweep" technique to scan threat tubes and track
each object separated from the chaff background by atmospheric
interactions. In monosweep, a cluster of MAR receiver beams was
simultaneously steered in angle and controlled in beamwidth so that
the threat tube was "swept" for signal returns after each
radar transmission. This technique, which used the flexibility of the
Modulation Scan Array Radar (MOSAR) beamforming and steering method,
produced receiver beam clusters whose width just matched the threat
tube width at each range that yielded a radar return. The signal
strength of objects in the threat tube was thus maximized at any
given range.

As
the reentering objects in the threat tube were resolved, their radar
signals would be processed to estimate their weights and ballistic
coefficients. SPRINT missiles would be launched to intercept
threatening objects as they were identified.

Deployment

The
NIKE-X system was modular, and the primary purpose of each module was
to defend a single urban area. Defense components would be allocated
to limit fatalities during those attacks designed to inflict maximum
fatalities. Secondary deployments included locating the MARs to
defend small cities and adjacent MAR modules.

Specific
deployments analyzed during the NIKE-X development ranged from
covering a relatively small number of cities, including no Small City
Defense (SCD) modules, to furnishing essentially total city coverage,
including a large number of SCD modules of various types. Each
deployment could be implemented in phases to achieve the highest
level of overall defense at any point in time.

Functional
Capabilities of Major Subsystems

This
paragraph briefly describes each major subsystem, emphasizing its
role and relationship with the whole.5

Multifunction
Array Radar (MAR)

MAR
was an L-band, high-power, phased-array radar that was NIKE-X's
principal sensor. It had four functions: (1) search and verification,
(2) threat evaluation, (3) target track, and (4) missile track. Its
multifunction capability was achieved through electronic beamforming
and steering controlled by programmed data processing equipment.

The
MAR had separate transmitting and receiving subsystems, with two
transmitting and two receiving arrays per radar. Each set of one
transmitting and one receiving array was effective over one quadrant
of the radar's combined 180-degree azimuthal coverage. Each array
consisted of a large number of cylindrical elements whose radiating
ends formed a planar face approximately circular in shape.

The
MAR could transmit signals of any of 14 different waveforms for its
several functions. These waveforms varied from single CW pulses of 1
to 440 microseconds length to chirped pulses and pulse trains. The
pulse trains were used for discrimination, with the most
sophisticated being a sequence of 32 coherent 6.2-micro-second
pulses, 12.4-microseconds apart with a 30-megahertz bandwidth. With
its long search pulse, the MAR could detect small objects in a
reentry complex as they crossed the radar horizon.

The
MAR receiver used a technique of electronic beamforming and steering
known as "modulation-scan" or MOSAR, which was described
under Operational Concept above.

Missile
Site Radar (MSR)

The
MSR was an S-band, single beam, phased-array radar that, depending
upon its defensive role, could be built with one to four phased-array
lens-type antenna faces. In all configurations, a single transmitter
and receiver time-shared the face(s). The MSR could transmit or
receive in one direction at a time as opposed to MAR's multifunction
operation. The four-faced MSR provided 360-degree azimuthal coverage.

The
MSR had four system functions: (1) search and verification, (2)
target track, (3) limited threat evaluation, and (4) missile track.
In the plan for Small City Defense, the MSR, along with its
associated data processor, performed all four of these functions.
When it was deployed as part of the MAR defense module, its role
would be primarily that of target and missile tracking. The MSR could
transmit any of six different waveforms, including short and long CW
pulses, a chirped pulse, and a pair of pulses for threat evaluation.

SPRINT
Missile

(IMAGE OF POOR QUALITY)

Figure
2-3. SPRINT Missile Firing

SPRINT
was a two-stage, solid propellant missile designed for short-range
intercepts inside the atmosphere. (See Figure 2-3.) It was intended
to be guided by radio command guidance from either the MAR or MSR,
but only the MSR guidance transponder was developed. Its first-stage
flight was controlled in pitch and yaw by a thrust vectoring system
in which liquid Freon [*] was injected into the booster exhaust.

[*
- Trademark of E. I. DuPont de Nemours.]

During
second-stage flight the missile was steered by aerodynamic forces
acting on air vanes. A pulsed transmitter in the missile served as an
S-band or L-band beacon, depending on the ground radar.

The
SPRINT missile was ejected vertically from an underground launch
station by a gas-powered piston. After it cleared the launch cell,
its first-stage motor was ignited; the second-stage motor was ignited
after the first stage burned out. SPRINT was a high-acceleration,
highly maneuverable missile that could intercept targets between 5
and 100 kilofeet high. A typical intercept would occur at an altitude
of 40,000 feet, at a ground range of 10 nautical miles, after about
10 seconds of flight time. See Chapter 9 for a more complete
description of this missile.

ZEUS
Missile

(IMAGE OF POOR QUALITY)

Figure
2-4. ZEUS Missile Firing

ZEUS
was a three-stage, solid propellant missile designed for long-range
intercepts with radio command guidance from either the MAR or MSR.
(See Figure 2-4. ) In the atmosphere, aerodynamic forces acting on
the third-stage control fins controlled steering. Outside the
atmosphere, gases expelled through the same fins controlled motion. A
pulsed transmitter in the missile was beacon tracked by the ground
radar.

The
ZEUS missile, launched from an underground station at an angle of 85
degrees from horizontal, was unguided until second-stage ignition.
The first and second stages had similar characteristics and
accelerated the third stage to peak velocity. The third stage carried
the warhead, missile guidance set, autopilot, fin servo system,
hydraulic system, and the thrust vector motor. See Chapter 1 for a
more complete description of ZEUS, and Chapter 10 for a description
of SPARTAN, the successor to the ZEUS missile.

A
typical ZEUS missile intercept, which would take place 100 nautical
miles above the tangent plane at a tangent range of about 300
nautical miles, would require a flight time of about 300 seconds. For
such an intercept, aerodynamic steering would remove trajectory
errors before the missile left the atmosphere. The missile would then
"coast" without guidance or thrust until third-stage
ignition. Controlling the third stage by thrust vector reaction would
remove residual trajectory errors just before intercept. For longer
range intercepts, the third-stage motor could be ignited earlier and
used to increase missile range at the expense of accuracy.

Data
Processor

There
were two general forms of data processor in NIKE-X: the Defense
Center Data Processor (DCDP) and the Local Data Processor (LDP). The
difference between them was in the number of modules (processors,
stores, display consoles, etc.) each contained. Because of its
modular design, the data processor could be sized for its particular
application at each site. Within each DCDP and LDP, the general
purpose Central Logic and Control (CLC) performed the computation and
central processing. Manual command and control was implemented by the
Display Subsystem (DSS).

Automatic
control was centered in the CLC. Computer programs, stored in program
stores, controlled NIKE-X system operations as interpreted and
executed by processor units. The processor units obtained input data
from variable stores and stored computation results there. Processor
units operated in parallel, forming a multiprocessor system in which
each processor, as it became idle, was assigned a computational task,
or program segment, to execute.

The
DCDP used separate report processors for routine initial data
processing of MAR radar returns. This wired logic preprocessing
relieved the CLC of many repetitive computations on a large amount of
data.

Nth COUNTRY DEFENSE STUDIES

Basic
to the NIKE-X concept, as it developed during 1963 and 1964, was the
idea of defending industrial and suburban centers against heavy USSR
attacks during the 1970s.4 The objective was to minimize
overall damage to the country.

The
cost of limiting damage against massive and sophisticated attacks was
relatively high, and only part of the population was protected. From
early 1965 to late 1967, increasing interest in potential "Nth
Country" or "light" attacks,5 as well as
developments in nuclear warhead technology, [*] led to a series of
studies and deployment options.

[*
- Applicable to ZEUS or modified ZEUS missiles.]

The
Nth Country or area defense concept evolved from those studies as a
defense against light attacks, along with concepts of terminal
defense,7 including defense of strategic forces. This
effort culminated in the NIKE-X 1-67 deployment concept,8
the harbinger of the SENTINEL System.

During
this time, there were significant changes in equipment concepts: the
PAR was conceived and its development commenced, the autonomous MSR
came into being, and the ZEUS DM-15C missile was extensively modified
to eventually become the SPARTAN missile.

Defense
Objectives

The
evolution of NIKE-X was naturally shaped by the evolution of defense
objectives, which were in turn shaped by prevailing economic,
political, and technological factors. Initially, the objective was to
blanket the Continental United States (CONUS) with a high-altitude
ZEUS-type defense, backed up at urban centers by a close-in SPRINT
defense.

By
the time of the 1-67 deployment study, defense objectives had
crystallized into two major roles, with some equipment elements
supporting both:

1. By minimizing the probability of penetration, the
defense was to deny damage in relatively light attacks. As the attack
force grew, the defense was to minimize population fatalities. Also,
modularity allowed growth from the original deployments against light
attacks to a damage-limiting defense against highly sophisticated
threats from any source.

2. The defense was to ensure that a significant
number of the Minuteman strategic missile force would survive a USSR
attack.

Threat
Description

An
Nth Country, lacking an extensive industrial base, could only attack
the U.S. with a limited number of relatively unsophisticated ICBMs
and SLBMs. It was assumed that this limitation would remain quite
stable, with the significant variants being the offensive force
level, RV vulnerability, and the number of SLBMs.

The
NIKE-X 1-67 Study assumed that up through 1980 the Chinese Peoples'
Republic (CPR) threat would simply be a single large, blunt warhead
accompanied by a tank and hardware pieces. Both the warhead and the
tank had large radar cross sections, since no attempt was made to
conceal either. After 1980, the CPR RVs would grow moderately in
sophistication and significantly in numbers.

Although
the later NIKE-X developments basically considered that the USSR
threat would be directed against Minuteman forces, NIKE-X nonetheless
was a factor in area defense because it had to defend the country
against accidental launches of USSR ICBMs. The postulated USSR
threat, although more sophisticated than the early threat, determined
the. eventual NIKE-X response with long-range interceptors.

Operational
Concepts

At
the beginning of this development period, it was considered that the
modified ZEUS missile would support the terminal defense of
industrial and urban centers. ZEUS missiles would disrupt
"penetration aids" (decoys, chaff, etc.) and allow the MAR
to gather data on RVs as early as possible.

By
the mid-1960s, the emphasis was to reduce the cost of defense, so new
directions for NIKE-X were evolving. At the same time, developments
in warhead technology altered the earlier concepts about the modified
ZEUS and gave it a significant capability for killing RV/ warheads
during attacks that included penetration aids. By this time the
possibility of light attacks was being considered, although concern
about sophisticated attacks remained dominant.

These
changes in emphasis eventually led to a less powerful MAR, designated
TACMAR, which could search for and track the basic NIKE-X threats at
long ranges. It could react early enough for modified ZEUS to
intercept threats and protect almost all of CONUS from the
unsophisticated threats. Around urban centers ZEUS would be backed by
SPRINT, which gave the cities two levels of defense. Because Nth
Country threats involved moderate to small RVs without penetration
aids, a VHF radar was required for long-range detection of these
attackers, thus complementing the TACMAR.

In
addition, to defend the U.S. against attacks from any direction and
for terminal defense, the proposed typical NIKE-X deployments
consisted of TACMARs, VHF radars, and ZEUS/SPRINT/MSR sites. (The
MTR-TTR combination of ZEUS intercept was no longer required.)7

Next,
further evaluation of these basic ideas led to the NIKE-X Deployment
Study (DEPEX), which organized the defense against attack from an Nth
Country and light attacks from the Soviet Union.9 The
basic objective was still to protect population and industrial
centers. Particular attention was given to countering the ballistic
missiles the CPR might eventually develop. The defensive deployment
was to grow so it could meet the more massive and sophisticated
ballistic missile threats arriving from any quarter. The DEPEX
concept by and large retained the basic characteristics described
above, and added a four-phase deployment sequence. The first phase
was about as described in the above deployment options, but more
extensive, while in the next three phases the terminal defenses grew
in steps.

Increasing
interest in very light deployments, at least during the initial stage
of deployment, led to the DEPEX "Phase 0," which, for the
most part, used modified ZEUS missiles, VHF radars, MSRs, and a few
SPRINTS.9 In addition, system studies showed that somewhat
higher frequencies for the long-range search radars would strike the
most cost-effective balance between susceptibility to nuclear effects
and the long-range detection and track of objects with small radar
cross sections. Concurrently, interest in defending the Strategic
Offensive Forces became stronger.

This
concept embodied the objective of denying damage to an early CPR
attack and provided a moderate high-level terminal defense for
Minuteman forces.8 It also allowed for growth to heavy
terminal defense.

By
this time, the needed long-range characteristics were embodied in a
new UHF radar called PAR. The design of the modified ZEUS was
stabilized and the missile was renamed SPARTAN.

The
1-67 deployment used a few PARs, moderate numbers of MSRs, and many
SPARTANs and SPRINTS. The MSR and SPRINT missile system defended the
Minuteman bases and were also collocated with each PAR site. The
remaining MSRs and SPARTANs were strategically located throughout
CONUS.

In
this system, PARs carried out long-range surveillance and target
tracking. In area defense, SPARTAN served as the primary interceptor,
tracked and guided by the MSR. SPRINTs were to be used only to defend
PARs, urban areas near the PARs, and Minuteman silos.

Generally,
targets would be detected first by the PARs. After they were tracked
for some seconds, their trajectories and impact points would be
determined and the defense battery would be designated. In SPARTAN
engagements, information on target intercept would be continually
refined and passed to the Missile Defense Center battery assigned the
engagement. This battery would launch and guide interceptors to the
appropriate point. The concept was a good cost-effective balance
between radars (PAR), radar resources (tracking requirements), and
lethal effects from the large-yield SPARTAN warhead.

1-67
deployment concepts represented the first real effort to set up a
nationwide ABM command and control system and set forth the
functional logic of a defensive engagement. The PAR would operate
somewhat independently, with built-in rules governing normal search
assignment, detection, verification, and track initialization. The
MSR was more closely coordinated (between MSRs) within a Missile
Defense Center region. In fact, one facet of NIKE-X at this point was
the increasing degree of intersite netting that furnished CONUS-wide
coverage with a few search radars.

With
minor modifications, the 1-67 deployment and its operating concept
led directly to SENTINEL and later to SAFEGUARD, as discussed in
Chapters 3 and 4, respectively. Many SAFEGUARD features and
characteristics had their origin in the 1-67 deployment concept of
NIKE-X, which marked a fundamental milestone in the evolution of
SAFEGUARD.

Modified
SPARTAN

Between
1968 and 1971, there were extensive studies of improving the SPARTAN
interceptor in its assigned role and in a role against more
sophisticated attacks.10 This effort is mentioned here
because it falls into the studies associated with area defense.

The
study explored the utility of a high-performance (higher than
SPARTAN), long-range, exo- and endoatmospheric interceptor that would
significantly reduce the number of MSR/missile sites required to
defend CONUS. New tactics and advanced intercept concepts were also
studied. However, cost-effectiveness considerations terminated the
effort in 1971.

DEFENSE OF STRATEGIC FORCES-TERMINAL HARDSITE DEFENSE

Between
1963 and 1969, Bell Laboratories postulated several systems for
defending hardened U. S. ICBM sites. The systems evolved in response
to specifications of the threat and trial deployments, and they were
examined from the standpoint of cost, component availability, and
effectiveness in achieving objectives.

The
primary objective of hardsite defense was to deter enemy attacks on
the U.S. strat-tegic ICBM offensive force. If deterrence failed, the
defense was to save enough Minute-man boosters that the U.S. could
carry out its post-attack policy. The defense was to be effective
against an advanced-technology threat including penetration aids.
Existing technology and components were to be used in the proposed
deployments as fully as possible.

One
of the first two hardsite systems proposed was designed to protect
sites in urban areas;1 the other to defend sites at remote
locations. A hardened site could be a command and communication
facility at a SAC base or a cluster of ICBM silos. In a later study,
only hardened silos having the Titan II and Minuteman forces and the
hardened defense elements were to be defended.2 In this
work other contractors' schemes were also reviewed. They ranged from
area/terminal defenses similar to the Bell Laboratories concept to
proposals for the autonomous defense of each silo (called "hardpoint"
defense).

The
last major Bell Laboratories study of hardsite systems resulted in
the proposed movable radar, or Virtual Radar Defense (VERADE) system,
which furnished extended terminal coverage through radar netting.11
In this approach, the radar antenna and transmitter would be
transported by rail and moved frequently among a large number of
hardened radar sites. VTRADE was an alternative to fixed radars and
was intended to increase the radar attack price. It recognized the
practical limits and cost of increasing radar hardness, introducing
redundancy, or using decoy radars to force the attacker to increase
the "throw weight" of his offensive missiles.

Each
hardsite study indicated that MSR technology would be adequate, and
each study increased the radar hardness levels. Early in these
studies it was recognized that both data processing and hardsite
requirements for radar netting and resource allocation would be
complex. Computers would have to use faster circuitry and different
organizational schemes to achieve the required throughput. The
interceptor proposed for each system was the SPRINT. Interceptors
with improved performance would counter a more sophisticated
attacking vehicle, which could maneuver to increase its chances of
penetrating the NIKE-X defenses.12

The
defense system design took into account uncertainties faced by the
attacker. These uncertainties were caused by the disturbed
environment created by his warhead bursts, target vulnerability, and
the presence of an active defense. Defense parameters that affected
system requirements included sure-safe and sure-kill hardness levels
for radars and silos, single-shot warhead kill probabilities, peak
traffic rates, and the attacker's targeting doctrine. From these
considerations and knowledge of the Soviet ICBM force, a threat was
specified. The ICBM force was sized, assumptions were made about
Multiple Independently Targeted RVs (MIRVs), only high weight-to-drag
RVs were included, and trajectory geometries were bounded. The
attacker's payload was estimated, his booster
availability/reliability was computed, and his warhead yield and
vulnerability to interceptor bursts were estimated.

The
threat was enhanced by penetration aids which included tank
fragments, precursor bursts, chaff clouds, traffic decoys, ECM, and
maneuvering RVs. Many possible ways to distinguish warheads from
penetration aids were considered, and many were found unsuitable.13

PARALLEL ELEMENT PROCESSING ENSEMBLE

As
studies of ballistic missile defense systems progressed, the
postulated threats expanded greatly in terms of the number of objects
arriving simultaneously and the sophistication of the penetration
aids. This increase in threat influenced ABM design and especially
increased the estimate of throughput needed for ABM data processors.

In
response, a new concept of architecture for the ABM data processor
was suggested.14

Because
a large part of the processing associated with radar tracking and
discrimination required that the same set of algorithms be repeatedly
applied to each object, parallel elements might carry on the
processing. In 1964, research began on a content-addressable memory
invented by Lee and Pauli of Bell Laboratories. This memory offered
an approach to the needed parallel processing, and a follow-on
development program supported by the Advanced Ballistic Missile
Defense Agency (ABMDA) led to the Parallel Element Processing
Ensemble (PEPE) concept.

PEPE
was a programmable, special-purpose computing machine that augmented
conventional sequential computing in ABM data processing. Processing
capacity was largely independent of traffic because an independent
parallel element was assigned to each object in track. Each parallel
element was, in fact, a small digital computer, with an arithmetic
unit and memory. In addition, each contained a special-purpose input
unit called a "correlator," which associated radar replies
with the appropriate track by simultaneously comparing each radar
reply with predicted track positions. Most of the control circuitry
was in an ensemble control unit, which was connected in turn to a
more conventional "host" sequential digital computer. The
host computer stored instructions for the parallel ensemble,
sequenced through them, and passed them to the ensemble control unit.
The host computer also did the processing that could be most
effeciently handled by a sequential computer.15

By
the mid-1960s, a study was under way to adapt PEPE to ABM. The intent
was to realistically assess feasibility and cost factors. Several
studies were launched, primarily in the areas of software development
and testing.

Hardware
Feasibility

Using
readily available components, a processor with 16 elements was built
with integrated circuits and tested with an IBM 360/65 as a host
computer. This "IC Model" of PEPE was used in the
demonstration tests discussed below. A study which showed the
feasibility of using more advanced large-scale integrated circuits in
PEPE was completed toward the end of the development project.16

Software
Development

Since
the job to be done by parallel processing elements would be done the
same way by a sequential computer, similar programming methods could
be used. A parallel version of FORTRAN, P-FOR, became PEPE's basic
programming language. P-FOR was supported by a compiler and an
assembler to convert programs into machine code. Also, programs could
be written for input to the assembler using PAL, the Parallel
Assembly Language.

The
language and software system were available well before any hardware
so that programs could be tested by simulation. The P44 precompiler
converted each operation on parallel data in a P-FOR program into a
DO loop on an array in a standard FORTRAN program. The FORTRAN
program could be readily tested on any machine with FORTRAN
capability.

In
addition to P44, which tested P-FOR programs at the source level, the
Parallel ABM System Simulation (PASS) simulated operation at the
machine level. PASS Tests I to IV, each testing a broader system,
were planned. PASS I and II demonstrated PEPE's capability for basic
ABM processing and were completed. PASS III and IV were replaced by
tests defined by ABMDA, as noted below.

Application
Studies

To
identify problems and evaluate the advantages of PEPE, several
specific applications were studied:17

• SAFEGUARD.
Routines planned for SAFEGUARD as developed in NIKE-X simulations
were converted to parallel form in PASS I and 11.18

• VIRADE.
As discussed previously under Defense of Strategic Forces, the VIRADE
concept added the problems of changing sites to the basic ABM
problems.19

• ABMDA
defined tests. For a final evaluation of PEPE as part of the Bell
Laboratories development program, ABMDA defined two systems: Zero
Order Software (ZOS) and Preliminary Hardsite Defense (PHSD). These
replaced PASS III and IV. The final PHSD demonstration was against a
threat defined by General Research Corporation and transmitted to
Bell Laboratories by data link from Santa Barbara, California in
interrupted real time. The PEPE system used in this test was the
16-element IC model supplemented by sequential simulation, and it
achieved essentially all the test objectives.20

Lessons
Learned

• The
ability of PEPE to carry a large, constantly growing portion of
SAFEGUARD data processing was established. The threat level defined
for the current SAFEGUARD System did not make PEPE cost effective.
Its cost effectiveness would have to be established for a given
threat, for a given ABM system, and with the current state of the
processor art considered.

• The
feasibility of increasing system capability by removing processing
from a sequential computer and assigning it to a parallel processor
was established.

• The
high level language, P-FOR, was found to be a powerful tool in
rapidly programming a complex system.

REENTRY MEASUREMENTS PROGRAMS A, B, AND C

The
NIKE-X Reentry Measurements Program (RMP), which spanned the interval
from 1960 to 1970, had the objective of developing discriminants for
conical RVs. The program used a straightforward phenomenological
approach, with tabulated comparisons of radar observable
characteristics as functions of vehicle size, shape, and ablator
material.

To
complete the program, a broad spectrum of targets was observed by the
radar, optical, and infrared sensors21 at the Eastern Test
Range (ETR), Kwajalein Test Site (KTS),22,23 and White
Sands Missile Range (WSMR).2' Most of the RMP flights were
full-scale reentry tests flown into the Kwajalein Test Range. The
NIKE -X program supplied many of the unique targets. Other targets
came from the Air Force Advanced Ballistic Reentry Systems (ABRES)
Studies, SAC Evaluation Missions, and the Navy Polaris Program.

The
RMP general test requirements were coordinated through the Tri-Agency
Technical Coordination and Operations Group (TATCOG), an Army, Navy,
and Air Force committee that set test objectives and planned
coordination. The responsibilities and contributions of the various
RMP groups were divided as follows:

The
RMP was divided into several significant phases. Initially, from 1960
to 1964, the NIKE-X Field Measurement Program (FMP)22;25,26
developed sensor techniques and discrimination technology. The
prime objectives developed then, which were changed very little in
the follow-on RMP, were to determine:

• The
observables associated with various targets, which would define the
sensor techniques for obtaining adequate discrimination measurements

• The
relationship between various target types and sensor measurements to
define effective discrimination techniques.27

From
approximately 1964 through 1966, the experiments labeled RMP-A
23,26,28 were concerned with the class of material used in
RVs.22,23 The primary objective was to search for and
evaluate discriminants.29

The
RMP-B program (1966-1970)23,28 sought to establish basic
theoretical understanding of reentry phenomena so that experimental
measurements and discrimination techniques could be extrapolated to
other possible threat sizes and variations.30-32 Another
area of RMP-B was the qualitative confirmation, through on-board
instrumentation,33 of basic reentry phenomena that could
not be measured from the ground.

RMP-C
was to consider advanced RVs. Before the target requirements were
specified, the program was terminated about 1970.

Target
Vehicle Summary

The
RMP used a series of reentry measurements vehicles, tactical
offensive weapons with penetration aids, and vehicles developed for
future offensive weapons.31 The Reentry Measurements
Vehicles (RMVs) were uniquely developed for the RMP.

Missions
and Data Reports

Bell
Laboratories issued a Target Measurements Report (TMR) on each
reentry measurement mission. These documents briefly summarized the
operation and outlined pertinent factual information. Data available
for continued analysis were listed, and plots, photographs, and
available reentry identification information were included. The TMR
data reports are available at the Reentry Data Facility at Calspan
Corporation, Buffalo, N. Y., a data repository maintained by the
Army.

MULTIFUNCTION ARRAY RADARS

The
MAR-I Program

(IMAGE OF POOR QUALITY)

Figure2-5.
Close-up View of MAR-I at White Sands Missile Range

In
the early stages of NIKE-X, 1963-1964, the Multifunction Array Radar
(MAR) was foremost among the relatively new radar concepts. This
radar was to be the major NIKE-X sensor, able to perform in many
operational modes in a high-traffic environment and to carry out
endo- and exoatmospheric engagements. The MAR's principal task was to
form and steer the multibeam clusters that would perform the radar
missions of search, track, discrimination, and guidance.35

By
that time, studies of phased array radars had progressed to the point
where the fundamentals of their antennas and beamforming were well
understood. A number of arrays had been built to demonstrate some of
their basic capabilities. Prior to MAR, however, these sensors had
been designed for a single function, principally that of target
acquisition and tracking.

By
1963 the NIKE-X program had reaped substantial benefits from two
experimental linear arrays, one employing the time delay steering
proposed by Sylvania, the other using a novel modulation scanning
technique developed by the General Electric Company.36
Early tests of these two arrays formed a technical base from which a
complete array radar feasibility effort was launched. This radar
complex was identified as MAR-I. The design, construction,
installation, and testing of MAR-I took place in the 1961-65 time
period. A close-up view of the installation at WSMR is shown in
Figure 2-5.

Development
tests of the radar, scheduled into 1965, determined how well the
equipment met design objectives and furnished data for design
improvements to the NIKE -X tactical model (MAR-II) planned for
installation at Kwajalein. The development program included extensive
antenna pattern measurements and beam stability checks to evaluate
the beamforming and steering concepts. Dynamic tracking accuracy and
multiple beam operation tests were also included.

Major
contractors and their responsibilities were:

1. Western Electric. Acted as prime contractor for
the MAR-I project under contract DA-30-069-AMC-333(Y).

2. Bell Laboratories. Held overall responsibility
for project management, including design, development, building
construction, test site operation, and system evaluation.

4. Sperry Rand Univac, St. Paul, Minn. Designed the
MAR-I Phase II digital computer, the associated Control Switch and
Buffer (CSB), and the computer programming.

Western
Electric and Bell Laboratories also designed and constructed some of
the MAR-I equipment.

Functional
Capabilities

The
MAR-I at White Sands was designed to perform the functions shown in
Figure 2-6 and to demonstrate fully automatic operation.35
Manual override and a full manual capability were included to
allow flexibility in testing. A tactical system would operate in two
modes: surveillance (the normal mode) and engagement (which began
after a target had been detected and classified as a threat to the
defended area). The automatic elimination of targets as
non-threatening, based on impact predictions or discrimination, was
never implemented in this radar.

In
the surveillance mode, the system performed two functions: search
(and detection) and verification tracking. In the engagement mode,
the system performed four functions: search (and detection),
verification tracking, precision tracking, and discrimination
sensing. Except when restricted by the operator, MAR-I automatically
carried out verification tracking assignments on all targets detected
in the search beam.

After
verification, a precision tracker was assigned to threats and used
the target position estimates generated by the verification tracker.
Except for a coded pulse that increased range resolution, precision
tracking was essentially the same as verification tracking. A
sub-beam cluster, positioned either automatically or manually to
cover a threat tube, obtained discrimination data. Threat tubes were
cylindrical volumes whose axes were parallel to the velocity vector
of the target. A Coherent Signal Processing System (CSPS) for
acquiring discrimination data was developed but never installed in
MAR-I. It was added to the Discrimination Radar (DR) at Kwajalein to
support the Reentry Measurements Program (RMP).

Figure
2-6. MAR Functional Capabilities

Figure
2-7. MAR-I Functional Block Diagram

System
Description

Operational
Concept

MAR-I
operations reflected the two modes, surveillance and engagement, in
which a tactical system would function.35 In the
surveillance mode, the radar beam scanned the total coverage volume
in less than 20 seconds. When a target was detected, the radar
returns were examined automatically to extract target position and
range rate (radial velocity) data. A verification track on the target
began when the range rate and position predictions satisfied
preselected criteria for range velocity and track initiation volume.
Search scanning continued independently of the other functions.

An
operator could overrule the automatic function to initiate
verification tracking manually on a target of his choice. In either
case, the successful verification of a threat changed the mode from
surveillance to engagement. In the engagement mode, search and
verification tracking continued at a faster search scan rate. In
addition, the precision tracking and discrimination functions became
available.

Discrimination
data were obtained by either manually or automatically positioning
the radar coverage of a threat tube. Each threat tube was divided
into subtubes, each formed by a separate radar beam. The widths and
center-to-center spacings of the beams were controlled as functions
of range to provide constant-volume coverage independent of range.
The discrimination transmitter beam was a single beam broadened to
illuminate the entire threat tube.

A
precision tracker was assigned and given target position estimates
from the verification tracker. Verification tracking was thus a
prerequisite for precision tracking and terminated after the
precision tracker locked on the target. Except for a
pulse-compression waveform that increased range resolution, the two
track processes were essentially the same.

MAR-I
was divided into ten major subsystems, as shown in Figure 2-7. They
are briefly described below.36

Transmitter
Antenna

The
transmitter antenna consisted of active elements forming a circular
planar array, with elements arranged as the vertices of equilateral
triangles. Each element was fed by an individual power amplifier in
the transmitter. The transmitter array was housed in a concrete dome
structure so that the array normal was elevated 38.5 degrees above
horizontal. MAR-I had one transmitter array.

Receiver
Antenna

The
receiver antenna consisted of elements in a circular array, each
element followed by a low noise preamplifier which was part of the
receiver. MAR-I had one receiver array.

Transmitter

The
final power amplifiers were specially-designed high-gain
traveling-wave tubes. Delay matrices consisting of switching diodes
and strip lines performed beamforming and steering. Search, track,
and discrimination pulses at different frequencies were transmitted
in a single pulse chain.

Receiver

The
receiver operated on three separate channels, one each for the
search, track, and discrimination functions. Each channel had its own
beam forming and steering circuits and its own unique beam and
cluster configuration. The incoming signals from the antenna elements
were fed through individual preamplifiers to power dividers which
provided signals to the three channels. After beam-forming and
steering, the three mixing circuits (search, track, and
discrimination) converted the RF signals to IF signals at different
frequencies. These signals were then amplified in the IF amplifiers
and sent to signal processing.

The
VPC processed the outputs of the receiver track detectors and video
amplifiers, converted the desired information to digital form, and
converted search and discrimination video to digital form for test
purposes. The pulse-compression networks for the precision track and
discrimination functions were part of the signal processing
subsystem.

Radar
Control

Radar
control, under instructions from central data processing and control,
coordinated and controlled some of the activities of MAR-I. It
generated and selected local oscillator frequencies and modulation
parameters and controlled the beamforming and steering networks.

Displays
and Recording

Operators
at display consoles monitored system operations and performed some
MAR-I functions which would have been automatic in a tactical MAR.
The MAR-I display and recording subsystem had four operator
positions, which monitored and reported on system status, con-trolled
search and track assignments, positioned the discrimination cluster
for sub-beam selection, and controlled recording.

Fault
Location and Monitoring

MAR-I
used a Fault Location and Monitoring (FLAM) subsystem for more
efficient maintenance and to minimize down time. The subsystem
monitored the system to detect faults, indicated the existence and
rack location of each detected fault, and automatically recorded
fault occurrences.

RF
Calibration and Monitoring

The
RF calibration and monitoring subsystem measured the overall
amplitude and phase transfer characteristics of individual channels
in the phased array. Various routines were measured for all
combinations of input channels and beam outputs, and faulty
components were located by these measurements. In most cases
measurements did not interfere with normal operations. In the
transmitter, the transmitted search pulses were used for monitoring;
in the receiver, a calibration pulse was inserted during ranging dead
time just before the next transmitted pulse.

Central
Data Processing and Control

The
Central Data Processing (CDP) and Control Subsystem had three basic
units: Control Switch and Buffer (CSB), Tape Buffer System (TBS), and
General Purpose Digital Computer (GPDC). The CDP sorted and routed
all data flowing between the GPDC and the other units of MAR-I and
also performed system timing.

The
TBS served as a buffer memory between the GPDC and input/output
devices. Output devices were magnetic tape units, flex-writers, and a
high-speed line printer. The former two units were also used as input
devices.

The
GPDC processed large quantities of realtime data, and the computer
operated in the fixed-point parallel binary mode with a 24-bit word
format. Instructions were single address with a minimum execution
time of 2.5 microseconds.

Multifunction Array Radar (MAR-II)

As
discussed earlier in this chapter, NIKE -X was to be an autonomous
system capable of fully-automatic, instantaneous, and effective
response to a wide variety of offensive tactics and intensities of
ballistic missile attack. Its main radar was to be the MAR. The MAR
combined search, verification track, discrimination, precision track,
and defensive missile track and guidance into a single phased array
operating at L-band.

By
mid-1967, the ABM defense objectives of NIKE-X were directed to
defending CONUS against light attacks. This shift from local defense
against high-traffic, sophisticated penetration-aided attacks
culminated in a decision to concentrate on the lower cost autonomous
MSR as the primary terminal defense sensor. On this decision the
development of MAR and its Kwajalein prototype (MAR-II) was
terminated.

Initially,
it was planned that NIKE-X would be tested at the Kwajalein Missile
Range and involve two phased-array radars: the MSR and the MAR.37
The latter was to have reduced capability, but could be retrofitted
to full MAR capability later. The Kwajalein version of the MAR,
designated MAR-II, was to be a single-faced (single transmitting
antenna array and single receiving antenna array) radar.

To
retrofit MAR-II with minimum down time, all of its transmitter and
receiver elements and associated cabling would be installed
initially. To reach full MAR capability, the additional transmitting
and receiving hardware, waveform generation equipment, signal
processors, etc., would be installed, checked, and then connected to
the antenna elements.

TACMAR

Originally,
two versions of the MAR were to be used in NIKE-X. The MAR was to be
a higher powered radar, with a full complement of transmitting and
receiving antenna elements. The second version, TACMAR,5,38
had only half as many active antenna elements as MAR for both
transmitting and receiving. TACMAR thus had approximately half the
power output, lower receiver performance, and a proportionately lower
range. It could produce fewer waveforms and therefore had a reduced
discrimination capability. This radar was designed to be cost
effective in the less demanding defense against an early, relatively
unsophisticated threat. It was to be used for high-confidence, early
detection of ensemble attacks, for detecting RVs with small radar
cross sections at intermediate ranges, and for supporting ZEUS area
defense and SPRINT local defense.9 If the need developed,
TACMAR could be augmented to full MAR capability.

MAR/TACMAR
Subsystems

MAR
and TACMAR were divided into six major subsystems, as shown in Figure
2-8. They are briefly described below.5,38

Figure
2-8. TACMAR Block Diagram

Antennas

In
TACMAR, each of the two transmitting antenna arrays contained active
elements arranged in a concentric hexagonal configuration with one
element in the center. In addition, passive elements were mounted in
the array face so that TACMAR could later be augmented to a full MAR.

Transmitter

The
transmitter chain generated and radiated high-power pulses and pulse
trains with the correct waveforms for various radar functions.
Real-time delay boards, with diode bit switches directed by radar
control, formed and steered beams. After high-power amplification by
traveling wave tubes, the signal went to the transmitting elements
through an RF face selection switch.

Receiver

The
output of each element of the receiving antenna array was connected
to a preamplifier module. The module had a transistor amplifier,
level control attenuators, a second transistor amplifier stage, and a
phase equalizer unit. The output of the module was connected to the
Beamforming and Steering (BFS) equipment which was of the
fan-multiplex MOSAR type. The BFS circuits steered the multiple beams
formed by the receiver. These circuits had an output for each of the
40 discrimination beams (nine of which formed the search cluster) and
the three monopulse track beams. Digital inputs from radar control
controlled the BFS equipment. The local oscillator signals, which
were used in the mixers to reduce the received L-band signals to
intermediate frequency, were formed in the exciter-stalo.

The
input module of the BFS section included the face switch directed by
radar control to switch receiver operation to either
antenna-preamplifier face. The received signal output from the BFS
section went to the signal processor.

Signal
Processor

The
signal processor accepted outputs from the receiver and converted
them to forms for the radar function that the Defense Center Data
Processing System (DCDPS) was analyzing. The signal processor also
accepted pulses from the missile beacon and identified or rejected
spurious signals introduced by noise, countermeasures, or sidelobes.

Radar
Control

Radar
control provided communications between the MAR and DCDPS. It
executed DCDPS's Central Logic and Control (CLC) orders concerning
pulse selection, transmitter and receiver BFS equipment, frequency
selection, and power levels. Radar control furnished timing
information to the subsystem elements and accepted fault location
information, which it relayed to the monitor.

Monitor

The
monitor detected system degradation, calibration drifts, or failures
that required replacement of a unit. Also, if the failed unit was a
critical item, the monitor took corrective action by switching in a
redundant unit. System degradation was reported via displays and
printouts. The monitor had two major parts: RF Calibration and
Monitoring (RFCM) and Fault Location and Recording (FLAR).

Conclusion

By
mid-1967, the ABM defense objectives of NIKE -X were directed to the
area defense of CONUS against light attacks. This shift from local
defense against high-traffic, sophisticated penetration-aided attacks
culminated in a decision to concentrate on the lower cost, autonomous
MSR as the primary radar for terminal defense. Hence, the development
efforts on MAR, the Kwajalein prototype (MAR-II), and TACMAR were
terminated.

As
stated earlier, the fundamentals of phased-array antennas and
beamforming were well understood when MAR-I was conceived, and the
only real question concerned the application of phased arrays to a
multiplicity of simultaneous functions. Thus, the paramount lesson
learned from MAR-I was that the program verified the analytical
predictability of array performance in a multifunction role.

Of
equal, if not greater, importance was identifying the significant
problems that resulted from attempting to verify hardware and
software on site, with an operational system, without the support of
either a hardware or software testbed. This was especially apparent
with the array hardware. Unit level tests of either single elements
or a small sampling of elements with their associated hardware
appeared to be trouble-free. However, when these tests were
integrated into the complete system consisting of thousands of
elements with their associated signal and power cabling, adverse
interactions occurred. A hardware testbed for simulating the physical
and electrical characteristics of a full array might have averted the
problem. Software testing presented a similar problem, since
development and test were done by computer simulations of the
expected data processor-radar hardware interface. A software testbed
that duplicated the interfaces would no doubt have uncovered most of
the problems with the on-site software installation. Partly because
of this MAR-I experience, the Tactical Software Control Site (TSCS)
concept was adopted for SAFEGUARD. TSCS called for the development,
integration, and evaluation of tactical software in a testbed that
duplicated the on-site data processors and radar interface hardware.

GUARDIAN (FORMERLY CAMAR) PROGRAM

During
the mid-1960s, measurements taken by field radars on reentering
bodies had shown an enormous growth in both quantity and
sophistication. This information strongly stimulated research in
discrimination techniques. Despite vigorous efforts to develop a
better theoretical understanding of the fundamental phenomena
involved in reentry, the physics of it remained largely an empirical
science. By 1968 the success of discrimination research created the
need to construct a real-time discrimination capability and to
demonstrate its effectiveness in a realistic traffic environment. To
demonstrate discrimination capability required a radar and
data-processing facility that could perform a variety of interactive
functions. It was not sufficient merely to implement, in real time,
the simple target-oriented discrimination techniques that were
successful in post-flight data analyses, because a credible ABM
discrimination depends on a sequence of interrelated events, such as,

• Determining
the bounds of the threatening complex to predict the bounds and
location of threat tubes to be searched for RVs

• The
automatic techniques which acquire and track objects as they emerge
from tank breakup clutter or chaff clouds

• The
ability to cope with large numbers of traffic decoys and deployment
hardware, so that the more likely RV objects can be identified and
scheduled for sophisticated discrimination processing

• The
ability to maintain track reliability in the presence of crossing
targets and nuclear perturbations

• Real-time
management of site resources (radar, data processing, and missile
stockpile) to effectively allocate them in the presence of traffic
overloads.

A
program (initially labeled CAMAR, for Common Aperture Multifunction
Array Radar, and renamed GUARDIAN) was started to identify the needs
of the ABM community and significantly advance understanding in these
areas of the discrimination system problem.

Program
Objectives

The
intent of the GUARDIAN (CAMAR) program was to produce the
technological base and experience from which an urban terminal or
hardsite defense system could be developed. The program involved the
development and implementation of a system testbed facility at Bell
Laboratories, Whippany, and a radar and data processor at Kwajalein
that could search, track, discriminate, and intercept actual
penetration-aided threats.

GUARDIAN'S
basic thesis was that the various ABM system functions could not be
developed outside the context of the integrated system.

Furthermore,
because of their complicated interdependence, these functions, taken
as a whole, could not be developed, integrated, and evaluated through
the usual approach of a prototype field site demonstration.
Therefore, to develop and evaluate the hardware/software forming the
integrated system, it was planned that a high-fidelity testbed be
built at Bell Laboratories in Whippany, N. J. All low-level radar
subsystems and a complete Data Processing and Control Computer (DPCC)
were to be incorporated in the testbed. To drive the test-bed, an
extensive radar simulator and threat generator were to be developed.

Thus,
the GUARDIAN proposition was (1) that the exploratory development
planned for GUARDIAN could only be accomplished with a flexible, high
fidelity testbed and (2) that the field site pseudo-prototype would
have two roles: to measure the environment and characterize radar
performance in supporting the testbed development, and to "certify"
testbed results through demonstration exercises.

With
these objectives, two distinct phases were planned for the Kwajalein
experience. The first was the Measurement and Recording (MR) role and
the second the Discrimination Demonstration (DD) role. The MR role,
primarily a real-time recording activity, was to supply supporting
data for developing the testbed and discrimination algorithms. The DD
roles were primarily concerned with demonstrating, in real time,
functions developed with the aid of the testbed.

Development
Progress

By
early 1968 the requirements for the testbed and its target and radar
environment driver had been established, and the testbed was under
development. This involved planning the interconnection of the data
processor, the low-level radar subsystems, and the radar
target/environment simulator. Target threats and specific target
environments were defined early in the program. The time-phased
sequence of missions to exercise and evaluate the system had also
been planned.

As
a consequence of the NIKE-X 1-67 (SENTINEL) decision, the very high
traffic, regional coverage capability of the MAR was no longer
needed. Therefore, in April 1968, the MAR/TACMAR development and the
MAR-II prototype work at Kwajalein were redirected to the GUARDIAN
program. MAR's basic elements were used in designing CAMAR, the field
site radar of the GUARDIAN program.39 The major subsystems
of CAMAR were:

• Array
Subsystem. This used a common aperture that functioned as both
transmitter and receiver. A beam steering translator controlled the
phase shifters and converted steering orders from the Data Processing
Control Computer.

• Transmitter
Subsystem. The waveform generator, exciter, and stalo were controlled
by the data processor. The radar control processor selected from
among six waveforms and associated signal processors.

• Receiver
Subsystem. The receiver input was a low-noise parametric amplifier.
The receiver was to form a three-beam cluster for search and
designation and a four-beam monopulse cluster that could be broadened
for track.

• Signal
and Report Processor. Individual processors were provided for the six
waveforms.

Development
Plan

GUARDIAN'S
MR role was scheduled for early 1972 and the DD role by late
1973.40,41 The test and evaluation phase was to consist of
two parts:

1. Testing the radar to ensure that it met
requirements

2. Evaluating the entire radar-computer system to
establish that it performed the DD role as intended.

Demise
of the GUARDIAN Program

By
early 1969 the program received the name GUARDIAN; its radar
continued to be designated as CAMAR. During this period serious
consideration was given to modifying the testbed objectives to
directly support deployment of advanced hardsite defense systems.42
This implied a possible change in the GUARDIAN radar. Therefore,
design of hardware and software sensitive to the choice of radar
frequency was curtailed from mid-June onward.43 This was
essentially the end of the GUARDIAN program. Shortly thereafter the
Army decided that design of a terminal ABM would proceed in
directions different from the GUARDIAN program in two significant
ways:

1. A
prototype of a site-defense system would be developed.

2. Recognizing
the inadequacy of the technological and phenomenological data base of
the discrimination and bulk filter functions, the Lincoln
Laboratories discrimination development and demonstration effort,
employing the Kiernan Reentry Measurement Site (KREMS) at Roi-Namur,
was to be accelerated.

With
this redirection toward a directly deployable system design, the
GUARDIAN exploratory program was set aside.